I had several glitches on my 9900 out of the box, tried the 7.0.540 for a month, still some glitches, now on 7.1 since 20 days, a lot less glitches.
Battery life, I think it is the same, very poor.
app memory, mine is empty, so plenty of memory, did not check difference.
all on all, it is good, would keep it